The purpose of this project is to prepare suicide-substrates (enzyme-activated irreversible inhibitors) for monooxygenases catalyzing biosynthesis or metabolism of hydroxysterols which may be involved in physiological regulation of cholesterol biosynthesis. The scope of the project comprises design, synthesis, and biological assay of inhibitors for the enzyme(s) mediating 14-demethylation of lanosterol, oxidative removal of sterol 4-methyl groups, and 25/26-hydroxylation of cholesterol. Principles for the design of potential inhibitor derive from successful inactivation in this laboratory of cytochrome P-450 enzymes involved in drug metabolism. Potential inhibitors, obtained by rational chemical synthesis, are to be evaluated in vitro using particulate rat liver enzyme preparations. Evaluation of the effect of inhibitors on target enzymes, and on 3-hydroxy-3-methylglutaryl CoA reductase levels in cultured HTC cells is envisioned.